Effects of swimming exercise and soybean supplementation on the immune functions of rats fed a high-fat diet.

1. In the present study, the effects of swimming exercise and soybean supplementation on the immune functions of rats fed a high-fat diet were examined. 2. Thirty-four male rats were randomly divided into four groups: (i) HS, a high-fat diet sedentary group (n = 8); (ii) HE, a high-fat diet exercised group (n = 9); (iii) SS, a soybean diet sedentary group (n = 8); and (iv) SE, a soybean diet exercised group (n = 9). The high-fat diet was composed of 35% carbohydrate, 20% protein and 35% fat. For the soybean diet, 3% crude soybean extract was substituted for the protein, carbohydrate and fat according to the energy content of the diet. In the exercise groups, rats swam for 60 min/day, 5 days/week for 4 weeks. 3. The subpopulation of CD4(+) cells and the CD4(+)/CD8(+) ratio did not differ significantly between the high-fat diet and soybean diet groups. However, the subpopulation of CD8(+) cells in the spleens of SS rats was significantly higher than that in the spleens of HS rats (P < 0.05). In addition, splenic interferon-gamma secretion in the SE group, with or without conconavalin A stimulation, was significantly increased compared with the SS group (P < 0.05 and P < 0.01, respectively). 4. These results show that regular endurance exercise training with soybean supplementation ameliorates splenic T cell-mediated immunity.